Khloe and Tristan hit up Malibu Hills Wednesday for a healthy hike and seemed to cement what everyone's suspected for some time -- they're back together. The old adage that couples that dress together, stay together may also be true ... 'cause they seemed to coordinate their sleek black outfits.

Tristan even gave his sports agency -- Klutch Sports Group -- some good pub. BTW, it appears 'KUWTK' cameras were also rolling during their hike ... so, it's also possible this was just a scenic location for a heavy convo you'll eventually see on the show.

As we reported ... Scott Disick confirmed -- albeit, accidentally -- Khloe and Tristan are back together with a since-deleted comment on one of Khloe's Instagram posts. Remember, Khloe and Tristan have been hanging out a lot in recent months. They've also been quarantining together, but we initially thought that was just to co-parent.

But, take note ... no sign of True on this hike.